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	<div id="winchm_template_title">Multiprocessor Syntax</div>
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	<div id="winchm_template_content"><div id="mainSection"><p>KD and kernel-mode WinDbg support multiple processor debugging. You can perform this kind of debugging on any multiprocessor platform.</p>
<p>Processors are numbered zero through <i>n</i>.</p>
<p>If the current processor is processor 0 (that is, if it is the processor that currently caused the debugger to be active), you can examine the other non-current processors (processors one through <i>n</i>). However, you cannot change anything in the non-current processors. You can only view their state.</p>
<h3><a id="selecting_a_processor"></a><a id="SELECTING_A_PROCESSOR"></a>Selecting a Processor</h3>
<p>You can use the <a href="#Bookmark2088"><b>.echocpunum (Show CPU Number)</b></a> command to display the processor numbers of the current processor. The output from this command enables you to immediately tell when you are working on a multiple processor system by the text in the kernel debugging prompt. </p>
<p>In the following example, <b>0:</b> in front of the <b>kd&gt;</b> prompt indicates that you are debugging the first processor in the computer.</p>
<pre class="syntax" xml:space="preserve"><code>0: kd&gt;</code></pre>
<p>Use the <a href="#Bookmark1969"><b>~s (Change Current Processor)</b></a> command to switch between processors, as the following example shows.</p>
<pre class="syntax" xml:space="preserve"><code>0: kd&gt; ~1s
1: kd&gt;</code></pre>
<p>Now you are debugging the second processor in the computer.</p>
<p>You might have to change processors on a multiprocessor system if you encounter a break and you cannot understand the stack trace. The break might have occurred on a different processor.</p>
<h3><a id="specifying_processors_in_other_commands"></a><a id="SPECIFYING_PROCESSORS_IN_OTHER_COMMANDS"></a>Specifying Processors in Other Commands</h3>
<p>You can add a processor number before several commands. This number is <u>not</u> preceded by a tilde (<b>~</b>), except in the <b>~S</b> command.</p>
<div class="alert"><b>Note</b>    In user-mode debugging, the tilde is used to specify threads. For more information about this syntax, see <a href="#Bookmark1928">Thread Syntax</a>.</div>
<div> </div>
<p>Processor IDs do not have to be referred to explicitly.  Instead, you can use a numerical expression that resolves to an integer that corresponds to a processor ID.  To indicate that the expression should be interpreted as a processor, use the following syntax.</p>
<pre class="syntax" xml:space="preserve"><code>||[Expression]</code></pre>
<p>In this syntax, the square brackets are required, and <i>Expression</i> stands for any numerical expression that resolves to an integer that corresponds to a processor ID.</p>
<p>In the following example, the processor changes depending on the value of a user-defined pseudo-register.</p>
<pre class="syntax" xml:space="preserve"><code>||[@$t0]</code></pre>
<h3><a id="examples"></a><a id="EXAMPLES"></a>Examples</h3>
<p>The following example uses the <a href="#Bookmark2004"><b>k (Display Stack Backtrace)</b></a> command to display a stack trace from processor two.</p>
<pre class="syntax" xml:space="preserve"><code>1: kd&gt; 2k </code></pre>
<p>The following example uses the <a href="#Bookmark2025"><b>r (Registers)</b></a> command to display the <b>eax</b> register of processor three.</p>
<pre class="syntax" xml:space="preserve"><code>1: kd&gt; 3r eax </code></pre>
<p>However, the following command gives a syntax error, because you cannot change the state of a processor other than the current processor.</p>
<pre class="syntax" xml:space="preserve"><code>1: kd&gt; 3r eax=808080 </code></pre>
<h3><a id="breakpoints"></a><a id="BREAKPOINTS"></a>Breakpoints</h3>
<p>During kernel debugging, the <a href="#Bookmark1980"><b>bp, bu, bm (Set Breakpoint)</b></a> and <a href="#Bookmark1975"><b>ba (Break on Access)</b></a> commands apply to all processors of a multiple processor computer.</p>
<p>For example, if the current processor is three, you can enter the following command to put a breakpoint at <b>SomeAddress</b>.</p>
<pre class="syntax" xml:space="preserve"><code>1: kd&gt; bp SomeAddress </code></pre>
<p>Then, any processor (not only processor one) that executes at that address causes a breakpoint trap.</p>
<h3><a id="displaying_processor_information"></a><a id="DISPLAYING_PROCESSOR_INFORMATION"></a>Displaying Processor Information</h3>
<p>You can use the <a href="#Bookmark2430"><b>!running</b></a> extension to display the status of each processor on the target computer. For each processor, <b>!running</b> can also display the current and next thread fields from the process control block (PRCB), the state of the 16 built-in queued spinlocks, and a stack trace.</p>
<p>You can use the <a href="#Bookmark2311"><b>!cpuinfo</b></a> and <a href="#Bookmark2231"><b>!cpuid</b></a> extensions to display information about the processors themselves.</p></div></div>	
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